oop - MATLAB 面向对象 : How do I call a method on an object of class A from inside a method in an object of class B?

Question

语言:

我正在 MATLAB 中编写面向对象的代码。我几乎编写了所有内容，现在在尝试对其进行测试时遇到了一个看起来非常基本的问题。

代码背景:

我有一个 Window 类和一个 Tracker 类。两者都是 Singleton 类的子类(即，它们具有私有(private)构造函数以确保仅创建类 Window 和类 Tracker 的一个实例)。

我实例化了它们中的每一个 - 所以我现在有一个 myWindow 和 myTracker 对象。

在我的主脚本中，我调用了一个方法 myWindow.isNewbead()。 isNewbead 是 Window 类的公共(public)方法。

就是这个场景。现在的问题:

问题:

在 isNewbead() 内部，我调用 myTracker.getpredictedPositions()。 getpredictedPositions() 是类 Tracker 的公共(public)方法。但是，当我运行这一行时，我收到一条错误消息，指出变量“myTracker”未定义。果然，我查看了变量工作区，那里唯一的变量是局部变量 INSIDE myWindow.isNewbead();

所以我现在有两个问题:

问题:

1. OOP 是否无处不在？也就是说，在不显式地将第一个对象传递给第二个对象的方法的情况下，是否可以从另一个对象的方法内部调用一个对象的公共(public)方法？这对我来说似乎很麻烦，因为我在每个方法中都使用了很多不同类的对象的属性和方法，所以我每次都必须传递数百个对象!

2. 如果这只是一个特定于 MATLAB 的问题(例如非静态变量的问题)，那么我该如何解决它？

非常感谢!

问候。

Answer 1

对于单例，该模式需要“一种无需创建类对象即可访问单例类成员的机制”。如果你传递类的实例，你就做错了。这是一个使用静态类和全局 appdata 空间的 Matlab 实现。有 another implementation确实有一个来自 File Exchange 的抽象父级, 但它将被 clear classes 删除。选择你的毒药。

classdef MySingleton < handle
%
%SingletonParent - A class to limit the instances created to one.
%
%There is a problem with matlab:
%   clear classes will clear just about any instance, even those stored in
%   persistent variables inside of functions.  This would close any opened singletons
%   To work around this, we have a method that creates an instance and assigns
%   it to the appdata structure.  This instance can be explicitly killed, but
%   clear all and clear classes will not kill it.  If you ever clear classes,
%   you will get several messages of this flavor:
%
%   Warning: Objects of 'MySingleton' class exist.  Cannot clear this
%   class or any of its super-classes.
%
%   because of the way we assign and store the singleton, you cannot make
% this an abstract parent
%
%   Also, any intialization must be done after you get the instance, since you
%   have to be able to create it without any data.
%

properties  (Constant)
    APP_DATA_NAME = 'MySingleton';
end %properties


methods (Access = private)
    function obj = MySingleton()
        %initialization code.
        %must be private to ensure getInstance call is the only link into it.
    end %Singleton
end%private methods


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
methods (Static)
    function out = getInstance()

    %getInstance - get/creates Singleton
    %
    %   stores the instnace such that it is immune to clear all/clear classes
    %
    %out = getInstance
    %Returns
    %   singleton instance.  if it does not exist, creates a default one, or passes the data to the ctor

    if ~isappdata(0, MySingleton.APP_DATA_NAME);
        obj = MySingleton;
        setappdata(0, MySingleton.APP_DATA_NAME, obj);
    end

    out = getappdata(0, MySingleton.APP_DATA_NAME);

    end %getMasterInstance()

end %static methods

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
methods
    %public methods that it uses to work.
end %PublicMethods



end %MySingleton Class